The present invention relates in general to a recording and/or reproducing apparatus for a magnetic tape cassette specifically suited for video tape recorders (VTR), and digital audio tape recorders (DAT). Further particularly, the invention relates to the construction of the recording and/or reproducing apparatus including the magnetic rotary head, back tension mechanism and so forth.
Recently, various magnetic tape cassettes applicable to recording and/or reproducing apparatus with rotary heads have been proposed. One such typical magnetic tape cassette applicable to recording and/or reproducing apparatus is disclosed in the European Patent First Publication No. 01 60 822, published on Nov. 13, 1985, and the British Patent First Publication No. 2, 155, 905, published on Oct. 2, 1985. In the recording method of VTR's or DAT's, the magnetic tape is helically wound about the rotary head drum and the recording tracks are formed on the tape obliquely to the longitudinal direction thereof. Signal data is formed or read the magnetic rotary head out of the recording track. This recording method is referred to as "helical recording". This type of recording and/or reproducing apparatus includes a rotary head drum, supply and take-up reel bases on which supply and take-up reels are respectively engaged and a reel base driving means for rotating either of the reel bases in the required direction according to the selected operating mode, a tape loading mechanism winding some of the magnetic tape about the head drum after extracting it from the magnetic tape cassette, a reel base braking means for stopping rotational movement of the reel base in a stop mode in which the tape running is stopped, a brake releasing means for releasing the braking force caused by the braking means, a capstan rotating at a relatively slow constant speed, a pinch roller rotating with the capstan to feed the tape therebetween, and a back tension applying means, such as a tension regulator arm having a tension regulator pin, to apply back tension to the tape by applying pushing force to a surface of the tape in the tape running mode, and so forth.
When the recording and/or reproducing apparatus is in recording or reproducing operation, the tape is run at a constant speed by the rotational movement of the capstan and the pinch roller in a tape forward direction wherein the tape is wound from the supply reel to the take-up reel, and the running speed of the magnetic tape is controlled so as to be constant by the tension regulator pin so that fluctuation of the tape running speed is prevented. On the other hand, when the recording and/or reproducing apparatus is in the fast forward (F/F) mode or rewinding mode wherein the tape is run at a high-speed, the tension regulator pin is moved away from the side surface of the tape and the take-up reel base or the supply reel base rotates in the tape winding direction at a high speed. As described above, such rotary-head-type recording and/or reproducing apparatus is composed of many relatively complicated mechanisms.
When the apparatus is operated in a reverse mode in which the tape is wound from the take-up reel to the supply reel. It is necessary that back-tension be applied to the surface of the magnetic tape between the rotary head drum and the take-up reel for preventing slack in the tape. For example, in the case of the auto music sanning mode which will be hereinafter referred to as an "AMS", of a digital audio tape recorder (DAT), the tape is run at a higher speed than in the reproducing mode. In the AMS mode, the tape is stopped the moment an identification code data indicative of a beginning position of a desired tape segment is detected by the detecting means. This identification signal will be hereinafter referred to as an "ID code". Generally, the data is stored in a plurality of linear data regions which are so called tracks. This ID code data is written in the track formed in the vicinity of the edge of the magnetic tape. It is difficult to stop the tape at the exact desired position when the ID code is detected, because of the inertia of the tape driving means. It is particularly difficult to stop the tape running when the tape is running at a high speed. Therefore, normally in the AMS operation of the recording and/or reproducing apparatus, after detection of the ID code at a high speed, the tape direction is reversed and scanned again at a medium speed and when the ID code is detected again the tape is stopped. In this operation, a slight difference between the desired tape stop position and the actual tape stop position may still be caused. In which case, the tape direction is reversed again and the tape is run at a low speed, and after detection of ID code at the low speed, the tape is stopped at the desired tape stop position. After this, the recording/reproducing apparatus is operated in the reproducing mode. Thus, as will be appreciated from the above, when DAT having an AMS function is operated in the AMS mode, it is necessary that the running speed of the magnetic tape be changed from a high speed to a medium speed and further to a low speed, and the tape running direction is changed a number of times. In the above high-speed running mode, the tape is drived by the reel base. In the medium and low speed modes, the tape is driven by rotation of the pinch roller and the capstan. In this type of system, the tape section between the pinch roller and the capstan tends to become slack when the tape is started. Therefore, it is necessary to apply a tensioning force to the surface of the tape. While the tape is running in the forward direction, tension is applied by the tension regulator pin to the magnetic tape for preventing slack. When the tape is running in the reverse direction, it is necessary to apply back-tension to the take-up side reel base. This kind of recording and/or reproducing apparatus does not include another pinch roller and another capstan between the supply reel base and the rotary head drum in addition to the pinch roller and the capstan between the take-up reel base and the rotary head drum, or a second tension regulator between the take-up reel base and the head drum, thus the number of parts, the cost, and the complexity of the apparatus can be kept low.
An electromagnetic mechanism is provided for moving a brake shoe into or out of contact with the take-up reel base. The brake shoe is operated into contact with the take-up reel base while the tape is running in the reverse modes. On the other hand, in other modes, the brake shoe is held away from the take-up reel base. In the prior art two electromagnetic servo mechanisms are required. One operates a pair of brakes that serve to stop the tape reels and other operates a tensioning brake. Such electromagnetic servo mechanisms are expensive, and a special control circuits are required for controlling them, thereby increasing the cost of the product and electric power consumption and limiting the compactness of the apparatus.